Practice question

Specificity in polymerase chain reaction arises primarily from sequence complementarity between primers and template. Each primer of 18-22 bases is designed to anneal uniquely to flanking regions of target locus under stringent annealing temperatures, thereby defining start and end of amplicon. dNTPs are generic building blocks, polymerase catalyzes extension indiscriminately, and template provides coding information but does not select region. Well-designed primers with unique sequences, appropriate GC content, and avoidance of repeats prevent mispriming, non-specific bands, and genomic cross-reactivity, ensuring specific amplification.